US President Barack Obama and UK Premier David Cameron pledged to keep up the pressure on Libya and other brutal authoritarian regimes today - but stressed they had "learned the lessons" from military adventures under Tony Blair and George W Bush.

In a joint press conference after a morning of talks – and before Obama addressed both houses of Parliament - the Prime Minister and president said the "unique" special relationship between their countries remained "essential" for ensuring global security.

They said there would be "no let-up" for Muammar Gaddafi until he stood aside and allowed the Libyan people to choose their own fate. There were also calls for democratic reform in Syria and Yemen.

But both men insisted that their partnership and approach differed sharply from the days when Mr Blair and Mr Bush were in office.

Mr Cameron said "every relationship between a prime minister and president is different".

"I would say both of us strongly believe in the special relationship. We both called it an essential relationship," he told journalists at Lancaster House in London.

"But we have to learn the lessons of history about how best you promote the values that we share.

"That means yes, going with the grain of cultures. It means yes, having a patient understanding that building democracy takes time.

"You have to work on the building blocks, and not believe it can be done in an instant."